$ sudo apt-get update
$ sudo apt-get install libunity-webapps0 

libunity-webapps0 is installed in your system.

Make ensure the libunity-webapps0 package were installed using the commands given below,

$ sudo dpkg-query -l | grep libunity-webapps0 *

You will get with libunity-webapps0 package name, version, architecture and description in a table

libunity-webapps0 package basic information: